A338714 Number of numbers of the form i*n with 1 <= i <= n and tau(i*n) = 6.
0, 0, 0, 1, 1, 2, 1, 1, 3, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 2, 0, 8, 2, 1, 1, 3, 0, 3, 1, 2, 2, 2, 0, 3, 2, 2, 0, 3, 0, 3, 1, 1, 2, 3, 0, 14, 1, 2, 1, 4, 0, 2, 0, 2, 2, 4, 0, 4, 2, 1, 0, 2, 0, 4, 1, 2, 0, 4, 0, 4, 2, 1, 1, 2, 0, 4, 0, 1, 2, 4, 0, 2, 2, 2, 0, 4, 0, 2, 1, 2, 2, 2
Offset: 1
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
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PARI
a(n) = sum(i=1, n, numdiv(i*n)==6); \\ Michel Marcus, Nov 11 2020
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Python
from collections import Counter from sympy import factorint def A338714(n): f = Counter(factorint(n)) return sum(1 for i in range(1,n+1) if (l:=tuple(sorted((f+Counter(factorint(i))).values())))==(1,2) or l==(5,)) # Chai Wah Wu, Oct 14 2023